It is known to provide seed drills in which a central seed container is arranged to feed seed to a plurality of row units, which each comprise a metering device for controlling the dispensed quantity of seed for achieving a predetermined mutual distance between plants forming part of a respective row.
WO2013180619A1 shows a system in which granular material is fed from a central container to a plurality of row units, which each have a buffer and a metering device.
U.S. Pat. No. 6,609,468B1 shows a system in which material is fed from a central container to a plurality of row units with the aid of an airflow, and in which the flow of air and material is reduced or restricted once a sufficient level of material has been reached in the buffer of the row unit.
There is a need for an improved feed device for feeding granular material from a main container to a dispensing unit. In general terms, there is a need for a feed device of the kind which is operationally reliable and easy to use. More specifically, there is a need for a feed device which is easy to switch between feeding of different types of granular material.